Effect of heat treatment on bonding characteristics and interfacial microstructures in explosively welded Ti/SUS430 stainless steel clad

Effect of heat treatment on bonding characteristics and interfacial microstructures in explosively welded titanium/SUS430 ferritic stainless steel clad was investigated. The average shear strength of the clad annealed at 1073K for 3.6 ks was 338 MPa and was equivalent to about 60% of that of an as-welded clad. The strength of the clad annealed at 1073K gradually decreased to 242 MPa with increasing holding time up to 360ks. The same tendency was obtained from the clad annealed at 1173K. On the other hand, the strength of the clad annealed at 1273K drastically decreased to 107 MPa with increasing holding time up to 360ks. The clad annealed at 1073 and 1173K yielded TiC layer at the bonding interface, while the reaction layer in the clad annealed 1273K consisted of TiC, FeTi, Fe₂Ti and χ (Fe₂₉Cr₁₃Ti₈) from titanium side. It was noted that chromium existed in the Fe₂Ti, which has wide solubility limit for chromium, and χ compounds formed at the SUS430 side. The TiC layer in the former clads acts as a barrier for diffusion of titanium, iron and chromium across the bonding interface and prevents the growth of intermetallic compounds. The clad formed TiC layer at the bonding interface preserved high bonding strength even after prolonged annealing.